Aerosol Formation Initiated by Oxidation of Limonene: A Comparison of Oxidant Chemistry

ANITA AVERY, Mitchell Alton, Manjula Canagaratna, Andrew Lambe, Aerodyne Research, Inc.

     Abstract Number: 311
     Working Group: Indoor Aerosols

Abstract
Reactions of volatile organic compounds (VOCs) with various radicals generates oxygenated VOCS (OVOCs) and secondary organic aerosol (SOA) species. However, depending on outdoor sources and human activities, a different oxidant will dominate the initial reaction and resulting products. Limonene is released indoors both in bursts as part of fragrances or cleaning products and at lower levels from outdoor infiltration. Here we compare chlorine radicals (Cl) and hydroxyl radicals (OH) that are emitted from bleach cleaning activities, and ozone (O₃) oxidation of limonene, using an oxidation flow reactor (OFR). The yield and chemical composition of OVOCs/SOA generated from these reactions were characterized with several online measurements, including an aerosol mass spectrometer (AMS), an extractive electrospray chemical ionization mass spectrometer (EESI-CIMS), and scanning mobility particle sizer (SMPS). We observe that in addition to Cl being highly efficient at oxidizing organic molecules, it also promotes the formation of condensable vapors compared to OH. Low-volatility limonene oxidation products such as C₁₀H₁₈O₅ were detected by the EESI to provide such molecular characterization of products to compliment the bulk organic aerosol measured by the AMS. Resulting aerosols were small, with a mode number size distribution generally below 50 nm. Maximum SOA yields were highest with limonene/Cl, followed by OH and O3. This work can help inform aerosol exposure during common indoor activities.